<?php
class Helper {

    private static $_instances = array();

    public static function &factory($helperName) {

        $className = APP_NAME . '_Helper_' . $helperName;
        if (!array_key_exists($className, self::$_instances)) {
            self::$_instances[$className] = new $className;
        }
        return self::$_instances[$className];
    }
}
